Methods and apparatus for multi-camera X-ray flat panel detector

ABSTRACT

Some aspects include a device comprising a plurality of cameras arranged in an array, each producing a signal indicative of radiation impinging on the respective camera, the plurality of cameras arranged such that the field of view of each of the plurality of cameras at least partially overlaps the field of view of at least one adjacent camera of the plurality of cameras, to form a respective plurality of overlap regions, an energy conversion component for converting first radiation impinging on a surface of the energy conversion component to second radiation at a lower energy that is detectable by the plurality of cameras, and at least one computer for processing the signals from each of the plurality cameras to generate at least one image, the at least one processor configured to combine signals in the plurality of overlap regions to form the at least one image.

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to ProvisionalApplication Ser. No. 61/297,416, entitled “Methods and Apparatus forMulti-Camera X-ray Flat Panel Detector,” filed Jan. 22, 2010, which isherein incorporated by reference in its entirety.

BACKGROUND

Digital Radiology (DR) is a technology that uses flat panel detectors toproduce digital X-ray images directly. DR detectors are substantiallybased on standard area (which developed historically from the productionline sizes of x-ray film and x-ray film cassettes) devices having amedium that transfers high energy X-ray photons into electrical chargewhich are distributed and segmented into a matrix of pixels forming animage. For example, the charge at each pixel location may be digitizedand the whole matrix of pixels forms an X-ray image of the convertedcharge. The X-ray image may then be transmitted and displayed on acomputer screen.

There are two main major technologies generally used in such flat paneldetectors: 1) direct digital detectors, where the X-ray photons areconverted directly into charge by a flat surface layer of specificmaterials such as amorphous Silicon or amorphous Selenium; and 2)indirect digital detectors where an energy converter layer is used toconvert the high energy X-ray photons into a very high number of lowerenergy light photons (e.g., photons in the visible spectrum). Theselower energy light photons may then be converted into electrical chargeby a large matrix semiconductor device. As discussed above, the chargeat each pixel location may be converted into a digital valuerepresenting an intensity of the pixel in the digital X-ray image.However, such DR flat panel detectors are expensive and relativelycomplicated to manufacture.

To reduce cost and complexity, the relatively expensive large areasemiconductor layers may be replaced with one or more semiconductorcameras. The cameras may be relatively inexpensive small area siliconpixel matrix cameras, such as those formed from arrays of charge-coupleddevices (CCDs). Thus, the lower energy light photons coming out of theenergy transfer layer (e.g., a phosphor screen) pass through a largelens and the image is focused on the small silicon chip to produce thetransfer to charge and then into a digital image.

SUMMARY

Some embodiments include a device comprising a plurality of camerasarranged in an array, each of the plurality of cameras producing asignal indicative of radiation impinging on the respective camera, theplurality of cameras arranged such that the field of view of each of theplurality of cameras at least partially overlaps the field of view of atleast one adjacent camera of the plurality of cameras, to form arespective plurality of overlap regions, an energy conversion componentfor converting first radiation impinging on a surface of the energyconversion component to second radiation at a lower energy that isdetectable by the plurality of cameras, and at least one computer forprocessing the signals from each of the plurality cameras to generate atleast one image, the at least one processor configured to combinesignals in the plurality of overlap regions to form the at least oneimage.

Some embodiments include a method comprising converting first radiationimpinging on a surface of the energy conversion component to secondradiation at a lower energy, receiving at least some of the lower energyradiation at a plurality of cameras arranged in an array, each of theplurality of cameras producing a signal indicative of radiationimpinging on the respective camera, the plurality of cameras arrangedsuch that the field of view of each of the plurality of cameras at leastpartially overlaps the field of view of at least one adjacent camera ofthe plurality of cameras, to form a respective plurality of overlapregions, and processing the signals from each of the plurality camerasto generate at least one image, the at least one processor configured tocombine signals in the plurality of overlap regions to form the at leastone image.

Some embodiments include a device comprising a plurality of cameras, anenergy conversion component capable of converting first radiation at afirst energy to second radiation at a second energy lower than the firstenergy, and at least one refraction component positioned between theenergy conversion component and the plurality of cameras to refract atleast some of the second radiation emitted by the energy conversioncomponent onto corresponding cameras of the plurality of cameras

Some embodiments include a method comprising converting first radiationat a first energy to second radiation at a second energy lower than thefirst energy, and refracting at least some of the second radiationemitted by the energy conversion component and receiving at least someof the second radiation at a plurality of cameras.

Some embodiments include using any of the devices above to determine alocation for high dose imaging. For example, the device(s) may furthercomprise at least one remote computer configured to selectively activateany of the plurality cameras. The method comprises performing a low dosex-ray exposure with a first set of the plurality of cameras activated toobtain a first low dose image. Performing one or more subsequent lowdose exposures with a different set of cameras activated to obtain oneor more subsequent low dose images, wherein the different set of camerasis chosen based at least in part on the first low dose image or one ormore of the subsequent low dose images.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conventional camera-based x-ray imaging device;

FIG. 2 illustrates a camera-based x-ray imaging device according to someembodiments;

FIGS. 3A-3E illustrate using a blocking component to block unconvertedx-ray radiation, according to some embodiments;

FIG. 4 illustrates using mirrors to prevent x-ray energy from enteringthe cameras, according to some embodiments;

FIGS. 5A-5D illustrate concepts related to overlap regions, according tosome embodiments;

FIG. 6 illustrates tiles forming an image with a plurality of imagelayers, according to some embodiments;

FIG. 7 illustrates concepts related to obtaining multi-layer images,according to some embodiments;

FIG. 8 illustrates a device for obtaining x-ray images, according tosome embodiments; and

FIG. 9 illustrates methods and apparatus for remotely activatingselective cameras to locate the correct region to perform relativelyhigh dose imaging, according to some embodiments.

DETAILED DESCRIPTION

As discussed above, camera arrays may be used as detectors for x-rayimaging. Applicant has appreciated that various technologies alone or inany combination may result in improved image quality, more efficientimage acquisition, more flexible imaging devices, and/or camera-basedimaging solutions provided at lower costs. For example, one or moreoptical technologies may be used to collect more light released from theenergy transfer layer to increase the signal-to-noise ratio (SNR),increased the detected quantum efficiency (DQE), and/or may focus orredirect light to reduce cross-talk between cameras, as discussed infurther detail below. One or more camera technologies may be used toreduce cost, increase SNR, DQE and/or to improve the quality and/orintegrity of resulting images. Camera array technologies describedherein may improve diagnosis and treatment and may be used to facilitatemedical procedures. The number and arrangement of cameras implemented inan array may be exploited to obtain higher SNR data and/or to allow foremphasis and/or suppression of desired subject matter in the image data.

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, methods and apparatus according to thepresent invention. It should be appreciated that various aspectsdescribed herein may be implemented in any of numerous ways. Examples ofspecific implementations are provided herein for illustrative purposesonly. In addition, the various aspects described in the embodimentsbelow may be used alone or in any combination, and are not limited tothe combinations explicitly described herein.

As discussed above, flat panel detectors using cameras to replacerelatively high cost semi-conductor layers may reduce the cost of DRimaging equipment. However, conventional designs using a camera-basedapproach have suffered from poor image quality. The image quality ofconventional solutions suffer, at least in part, because lightcollection may be relatively inefficient, resulting in poor DQE for theimaging device. Some of the inefficient light collection may beattributed to the distance between the energy conversion component andthe cameras collecting the light emitted from the energy conversioncomponent. This distance may be dictated by the focal length of thecameras employed as sensors in the camera array.

As a result, only some fraction of the light emitted by the energyconversion component reaches the lens and is registered to form thecorresponding part of the image, negatively impacting the DQE of thedevice. In addition, because the lower energy photons released from theenergy conversion component are emitted in all directions, not only arephotons being lost as a result of the distance between the energyconversion component and the lenses, but some portion of the emittedphotons actually register in neighboring or remote cameras, resulting incross-talk that shows up as artifacts in the image.

FIG. 1 illustrates schematically some of the drawbacks of conventionalcamera implementations. Image sensor 100 includes a energy conversioncomponent 110 and an array of cameras 120 such as an array of CCDcameras. High energy radiation 105 such as x-ray radiation (e.g., x-rayradiation that has passed through an object being imaged) impinges onthe energy conversion component 110. The energy conversion component 110converts the high energy radiation to low energy radiation 115 (e.g.,photons in the visible light spectrum) due to the interaction betweenthe high energy radiation 105 and the material of the energy conversioncomponent 110. The energy conversion component may be made of anymaterial capable of suitably converting the radiation, such as aphosphor layer or other material that emits lower energy radiation inresponse to absorbing x-ray radiation.

As discussed above, the low energy radiation is emitted from the energyconversion component at all directions. As a result of thisomni-directional emission, coupled with the distance between the energyconversion component 110 and the cameras (e.g., as dictated by the focallength of the lens), substantial amounts of radiation are either lost orare detected by the incorrect camera. The resulting image may be ofrelatively low quality, having low SNR, DQE and/or may includerelatively substantial cross-talk artifacts as schematically illustratedin FIG. 1.

Applicant has appreciated that by improving the light transfer betweenthe energy conversion component (e.g., phosphor layer or screen thatconverts high energy X-rays to lower energy light photons in the visiblespectrum) and the cameras, image quality may be improved. FIG. 2illustrates an image sensor according to some embodiments. Image sensor200 includes a number of improvements that may be used either alone orin any combination to facilitate improved light transfer. Oneimprovement includes the addition of refractive layer 230 to address, atleast in part, the omni-directional (or at least 2π) emission of lowenergy radiation (a phenomena also referred to as “flare”). Therefraction component 230 may be a high refraction layer or highdispersion layer (e.g., a high refraction coated glass) placed betweenthe energy conversion component 210 and the cameras 220.

The refraction component operates to suppress (e.g., reflect) photons atangles larger than a critical angle (i.e., angles sufficiently far fromthe surface normal to the energy conversion component) to prevent flatangle photons from registering at neighboring or remote cameras, and tobend photons emitted at angles smaller than the critical angles (i.e.,angles sufficiently near the surface normal to the energy conversioncomponent) “inwards” to increase the amount of light that enters thelenses of the corresponding and appropriate cameras.

The refraction component 230 may be formed of a glass layer, a coatedglass layer, multiple layers of glass and/or other material layers,individual refractive lenses or any other suitable configuration orrefractive material that facilitates directing the emitted light to thelens of the correct camera. The refraction component 230 may be includedto improve the SNR by increasing the amount of light reaching theappropriate camera (signal) and decreasing the crosstalk (noise). Inaddition, since more of the emitted radiation from the energy conversioncomponent 210 reaches and is collected by cameras 220, the DQE of theimage sensor also may increase.

As discussed above, the distance between the energy conversion componentand the cameras in conventional image sensors allows valuable signal toeither go undetected or be detected by the incorrect camera. Thedistance in conventional designs is, at least in part, dictated by theparticular camera being used. In conventional image sensors, the CCDbased cameras require a relatively significant distance to accommodatethe focal length of the cameras, thus resulting in generally poor imagequality due in part to the physical limitations of the camerathemselves.

Applicant has appreciated that benefits of complementary silicon-oxidesemiconductor (CMOS) cameras (e.g., flat lens CMOS cameras frequentlyused in cellular telephones) may be used to facilitate less expensiveimage sensors, without a reduction in image quality, and in some caseswith improved image quality. Traditionally, CMOS cameras were perceivedto produce images of insufficient quality for purposes of DR andtherefore CCD cameras were selected as the only useable sensor solution.However, Applicant has appreciated that at least some of the advantagesof CMOS cameras may be exploited not only to solve some outstandingissues of conventional image sensors for DR, but to deliver images ofthe same or greater quality as images obtained using CCD camera arrays.

One advantage of CMOS cameras is the decrease in focal length. Applicanthas appreciated that this reduced focal length may be employed toposition the CMOS cameras and the energy conversion component closertogether, as schematically illustrated in FIG. 2. As a result, more ofthe light emitted from the energy conversion component will impinge uponthe correct camera, instead of being missed altogether or detected by anadjacent or nearby camera. Another advantage of CMOS cameras are thatthey are less expensive to manufacture than CCD cameras. Therefore, manymore CMOS cameras may be included in the sensor array without increasingthe costs of the DR image sensor. As schematically illustrated in FIG.2, additional CMOS cameras can be added to the array so that more of theemitted light is detected by one of the cameras in the array.

A further advantage of CMOS cameras is that they are smaller in size. Asa result, more cameras can be positioned in a given area than with CCDcamera solutions and the image sensor can be more densely populated withcameras, thus more optimally detecting the light emitted from the energyconversion component 210. Additionally, the smaller size (and lowercost) allows the cameras to be positioned such that multiple camerasdetect at least some light for any given pixel. This overlap has manysignificant benefits, as discussed in further detail below. It should beappreciated that any CMOS camera may used in embodiments employing CMOScameras, as the aspects are not limited in this respect.

Thus, as discussed above, Applicant has appreciated that using CMOSand/or flat lens technologies (e.g., camera technology similar to thatused in cellular phones) may allow the cameras to be placed closer tothe light emitting surface, thus increasing the light collection andimproving image quality. In addition, the relative inexpensiveness ofthese technologies allows more cameras to be used, thus furtherdecreasing the distance between the camera lenses and the light emittinglayer. Use of CMOS/flat lens cameras allows more cameras to be utilizedin a relatively inexpensive manner and allows the cameras to be broughtforward in closer proximity to the energy conversion component. The useof CMOS/flat lens technologies may be used alone or in combination withthe optical technologies herein above to increase SNR, DQE, reducecross-talk and/or otherwise improve image quality.

A further problematic issue with conventional image sensors that mayeffect image quality and/or the operation of cameras in the image sensoris unconverted high energy radiation that penetrates the energyconversion component. In particular, some of the high radiation energyimpinging on the energy conversion component may pass through withoutbeing converted to low energy radiation. As a result, this unconvertedhigh energy radiation may impinge on the cameras and damage theelectronic components, generate errant noise in the cameras or both.Applicant has appreciated that providing a blocking component ofmaterial that blocks at least a portion of this high radiation mayprevent some or all of the unconverted high energy radiation fromreaching the camera and/or associated electronic components of the imagesensor.

FIGS. 3A-3E illustrate blocking components suitable for reducingpotentially deleterious and/or harmful high energy radiation fromreaching the electronics of the imaging device. FIGS. 3A and 3Billustrate two embodiments wherein a separate blocking component 340 isprovided before and after the refraction component 330, respectively, toblock at least some of the unconverted high energy radiation. Blockingcomponent 340 may be made of a leaded glass or other material capable ofabsorbing relatively high energy radiation such as x-rays.

FIGS. 3C-E illustrate embodiments wherein blocking component 340′ isprovided as a coating on the refraction component 330, on the topsurface, the bottom surface and both surfaces, respectively. The coatingmay be made from a leaded material or other material coating capable ofabsorbing at least some of the unconverted high energy radiation.Alternatively or in addition to the blocking components described above,a blocking component (e.g., a block layer or blocking coating) may beadded to the lenses of the cameras to prevent high energy radiation fromreaching the light sensitive areas and/or electronics of the camera. Theblocking component may be made of material that is completely orpartially transparent to the lower energy radiation emitted from theenergy conversion component.

According to some embodiments, mirrors are used to prevent unconvertedhigh energy radiation from impinging on the camera and/or cameraelectronics. For example, in FIG. 4, the cameras 420 are arranged suchthat surface normal of the lens is directed substantially perpendicularto the surface normal of the refraction component 410. A mirror 440 madefrom material that reflects lower energy radiation 415 and passes higherenergy radiation 405 is positioned such that the lower energy radiationis reflected into the camera lens, while the higher energy radiation 405passes through the mirror and does not enter the camera and impinge onthe sensitive areas and/or electronics of the camera. The embodimentillustrated schematically in FIG. 4 may be used alone or in anycombination with the other techniques described herein for preventingunconverted high energy radiation from entering the camera and/ordamaging the sensor electronics.

As discussed above, in order to prevent flare and glare of the lightcoming out of the energy conversion component (e.g., the phosphor screenor photon convertor) that converts the high energy X-ray photons intothe lower energy seen light photons, the photons from each point on thephosphor screen are emitted in the 2 pi directions causing noisereferred to as flare. In addition, the light reflected from the lensesis reflected back by bouncing from the white reflective face of thephosphor screen causing another component of optical noise referred toas glare.

In conventional camera-based solutions, cameras are distributed andarranged such that their combined viewing area covers the full imagearea of the light emitting surface with some overlap between eachneighboring camera (to allow for stitching algorithms to stitch all theimages together to produce one continuous large digital image). Costconsiderations in conventional camera-based solutions limit the numberof cameras used. In addition, the size of conventional CCD cameras andthe associated electronics for transferring charge from the CCD elementsphysically limit how close together adjacent cameras may be positioned.As a result, the cameras have to be placed at a further distance fromthe light emitting layer, resulting in unnecessary loss of signal andincrease in noise from cross-camera registration.

In camera-based systems using an array of cameras to capture an image,each individual portion of the whole image captured by individualcameras must be combined together to form the whole image. This processis referred to as “stitching” due to its conceptual similarity tostitching together the pieces of a quilt to form the entire quiltedblanket. Conventional camera-based systems arrange the camera array suchthat the field of view of adjacent cameras are slightly overlapping.Typically, the overlap region is used to register the data to determinehow adjacent sub-images should be aligned for stitching. Numerousstitching algorithms are known to stitch together sub-images fromadjacent cameras to form the full images. Applicant has appreciated thatoverlap regions may be used for a number of purposes other thanstitching including, but not limited to, increasing SNR, improving imagequality and/or performing image enhancement, as discussed in furtherdetail below.

FIGS. 5A and 5B illustrate the fields of view for two cameras and fourcameras, respectively, positioned such that their fields of view haveone or more overlap regions. For example, FIG. 4A illustrates a field ofview 510 a representing the portion of an image sensed by a first cameraand a field of view 510 b representing the portion of an image sensed bya second camera. Due to the positioning of the cameras, there is a smalloverlap region 520 where the two cameras “see” substantially the sameinformation (i.e., both cameras are sensing the same portion of theimage). Because both cameras will capture highly correlated imageinformation in the overlap region, this region may be used to registeror match the data so that the two separate images can be aligned forstitching. FIG. 4B illustrates the overlap region for four fields ofview 510 a, 510 b, 510 c and 510 d of four adjacent cameras and thecorresponding overlap region 520 for any two adjacent cameras, andoverlap region 530 where all four camera's fields of view overlap.

It should be appreciated that the illustrations in FIG. 5 are schematicand the fields of view and overlap regions are provided to illustratethe concept of overlapping fields of view. However, the fields of viewand overlap regions may be of any size or shape (e.g., the fields ofview may be circular or polygonal and therefore generate differentshaped overlap regions) depending on the properties, positioning and/ortypes of the cameras used in the camera-based image sensor. Theprinciples described herein are suitable for fields of views and overlapregions of any shape and/or size, and the aspects are not limited inthis respect.

As discussed above, Applicant has appreciated that this overlap regioncan be further utilized to increase SNR, DQE and/or to perform imageenhancement. In connection FIG. 5A, the first and the second camera haveboth captured substantially the same information in the overlap region520. As such, there is approximately twice the information (i.e.,approximately twice the signal) in the overlap region. Referring to FIG.5B, the overlap region 520 has twice the signal and overlap region 530has substantially four times the signal. The additional information inthe overlap regions may be used to increase the SNR by combining thedata in any number of ways including summing, averaging, weightedaveraging or any other suitable operation that makes use of theadditional data available in the overlap region. Alternatively or inaddition to any number of linear combinations, non-linear combinationsof the data in the overlap regions may be used, as the aspects are notlimited in this respect.

As discussed above, the use of CMOS/flat lens technology cameras allowsfor a higher density of cameras to be arranged in a given area. Thus,the cameras may be positioned closer together. Applicant has appreciatedthat not only does this increase the DQE (e.g., by collecting more lightemitted from the energy conversion component), but the increased densitymay be such that the field of view of adjacent cameras can overlap toany desired extent. For example, in FIG. 5C four cameras have beenpositioned such that substantial portions of the field of view form theoverlaps region 530. In FIG. 5D, four cameras are positioned such thatthe overlap region 530 is substantially the entirety of the fields ofview of the cameras. For example, overlap region 530 may correspond toone portion or “tile” of a full image, and each camera may separatelycapture the entire sub-image corresponding to the tile. Applicant hasappreciated that by forming an image entirely from such tiles, eachpixel in the image can be formed from the information captured bymultiple cameras (e.g., 2, 4, 6, 8 cameras, etc.).

FIG. 6 illustrates a portion of an image formed from tiles substantiallyproduced by overlap regions of two or more adjacent cameras. Forexample, tiles 630 may be similar to image tile 530 in FIG. 5D formedfrom the overlap region of four adjacent cameras. However, image tilesmay be formed from overlap regions of more or fewer adjacent cameras, asthe aspects are not limited in this respect. In addition to imagequality improvement achieved from the increase in signal and reductionof noise, the overlapping field of views may be exploited to performimage enhancement such as emphasizing and/or suppressing selectedsubject matter from the images and/or performing dual energy imaging, asdescribed in further detail below.

In some embodiments, the cameras are disposed in number and proximitysuch that each pixel in the resulting full image (i.e., fully stitchedimage) will result from data from at least two cameras. The resultingimage will have improved DQE enabling the choice between dose reductionor improved image quality (for the same dose). Since each pixel locationis covered by at least two cameras, the resulting data will have atleast two arrays of data representing the entire image. These “layers”may be used in a number of ways to improve image quality, reduce doseand/or facilitate various imaging procedures, as discussed in furtherdetail below. Further benefits may be achieved using a camera arraylayout wherein more than two cameras cover each pixel location in theimage, thus improving light collection, image quality, increasing theDQE and/or enabling various image enhancing techniques.

As discussed above, by arranging cameras in number and proximity,multiple cameras can obtain data for each pixel location in an image. Asa result, the cameras will capture multiple independent images of thesame object (e.g., a patient undergoing medical imaging). Eachindependent image obtained from the camera array using such overlappingcameras is referred to herein as a layer. For example, in an exemplarygrid layout shown in FIGS. 7A-7C, the even and odd cameras may beutilized to obtain a multi-layer image. In FIG. 7A, the odd rows ofcameras 710 (denoted by white circles) and the even rows of cameras 720(denoted by black circles) may each capture a respective image layer toprovide a two layer image by overlapping the fields of view of adjacentrows. It should be appreciated that if the fields of view overlap to acertain extent, each layer will represent a version of the entire image(i.e., multiple images will be obtained).

Similarly, as shown in FIG. 7B, the odd columns of cameras 730 (denotedby the black circles) and the even columns of cameras 740 (denoted bythe white circles) may capture the respective layers to provide a towlayer image by overlapping the fields of view of adjacent columns. InFIG. 7C, both odd/even columns and odd even rows are utilized to capturea multi-layer image. In particular, odd column and odd row cameras 750(denoted by the white circles) may capture a first layer, odd column andeven row cameras 760 (denoted by the diagonal hatched circles) maycapture a second layer, even column odd row cameras 770 (denoted by thecross-hatched circles) may capture a third layer, and even column evenrow cameras 680 (denoted by the black circles) may capture a fourthlayer. By positioning the cameras appropriately, any number of layersmay be captured up to the physical limitations of the camera dimensionsand fields of view. It should be appreciated that the grid arrangementis merely exemplary and any other pattern may be used such as circularor honeycomb patterns, as the aspects are not limited to the number oflayers or the pattern of overlapping cameras.

As discussed above, the layers in a multi-layer image may each comprisea complete image of the object being imaged. This “redundant”information may be used to increase the SNR (e.g., by summing the layersto increase the amount of signal in the final image) and to increase theDQE (e.g., the increased density of cameras may optimize the percentageof light emitted by the energy conversion component that is detected byat least one of the cameras, rendering the image sensor increasinglyefficient). In embodiments using CMOS cameras, such techniques may becapable of producing images of higher quality than solutions thatutilize more expensive CCD cameras, however, improved image quality isnot a limitation or a requirement.

As discussed above, the multiple layers may also be used to performimage enhancement, such as emphasis and/or suppression of particularsubject matter of interest (e.g., emphasis/suppression of either hard orsoft tissue in the body). Techniques for image enhancement include bothspatial and temporal techniques, which may be used alone or in anycombination to assist in enhancing the images as desired. Applicant hasappreciated that image enhancement via emphasis/suppression of selectedtissue may be achieved, at least in part, by controlling the gain on thecameras either spatially (e.g., using different gains for cameras indifferent layers) or temporally (varying the gain over an acquisitioncycle) or both, as discussed in further detail below.

X-ray radiography is typically performed by detecting the extent ofx-ray attenuation caused by the various regions of the object exposed tothe x-ray radiation. Higher density material will attenuate the x-rayradiation to a greater extent than lower density material. Thus, in thebody, hard tissue such as bone and cartilage will attenuate x-rays to agreater extent than softer tissue such as the organs. At the detector(i.e., camera), the hard tissue therefore corresponds to less radiationimpinging on the detector (resulting in a smaller magnitude signal fromthe cameras) and soft tissue corresponds to more radiation impinging onthe detector (resulting in a larger magnitude signal from the cameras).Using this understanding, Applicant has appreciated that the gain on thecameras may be controlled to selectively emphasize/suppress subjectmatter of desired density. In particular, the higher the gain, the morethat hard tissue (e.g., bone, cartilage, etc.) will be emphasized andthe lower the gain, the more the hard tissue will be suppressed and thesoft tissue emphasized.

CMOS cameras have a useful property in that the gain on each camera maybe individually controlled. That is, the gain on each individual cameramay be set to a desired level. Applicant has appreciated that settingthe gain of cameras in each respective layer of a multi-layer image canprovide layers with different ranges of density material beingemphasized or suppressed. The multiple layers may then be combined inany number of ways to enhance the image by either suppressing certainmaterial to better observe subject matter of interest and/or emphasizingcertain material so that it appears more prominently in the image. Assuch, the individual camera gains can be used to perform selective imageenhancement. Such techniques may provide physicians, diagnostitians orother medical professions with images that are better suited forobserving the subject matter of interest for a particular medicalimaging application or procedure.

Referring back to FIGS. 7A-7C, the cameras in the respective layers maybe set to desired gains to perform image enhancement. For example, inFIGS. 6A and 6B, the even rows/columns may be set with a relatively lowgain and the odd row columns may be set to a relatively high gain tocapture layers with different density materials emphasized/suppressed.In FIG. 7C, each of the four layers may be set with a different gain tocapture layers with even richer image enhancement capabilities.Alternatively, for the purposes of image enhancement, the four layers inFIG. 7C may be grouped into two different gains (e.g., the layersassociated with diagonal cameras may be given the same gain) to capturefour layers of images with dual gain information. It should appreciatedthat gains set for the multiple layers in a multi-layer image may be setto any desired level using any desired combination or pattern ofcameras, as the aspects are not limited in this respect.

As discussed above, image enhancement may also be performed by varyingcamera gains temporally. As a general matter, direct radiography using acamera-based solution often involves integrating the camera signal oversome interval of time (e.g., an interval substantially the same as theduration of the x-ray exposure) to obtain the “value” corresponding tothe amount of light detected for the corresponding pixel (i.e., thecamera signal is summer over a given interval to give the pixel valueassociated with the corresponding camera). However, in CMOS cameras, theinterval over which the signal is integrated can be selected as desired.As a result, the duration of an exposure can be divided into multipleintervals over which the signal is integrated to give multiple outputvalues from each camera. Each interval, or designated intervals, may beassigned different gains. As such, each camera can have multiple signalsfor a single exposure, each set at a different gain level. As a result,each camera may produce multiple outputs at different gains for a singlex-ray exposure.

As a simple example, during a single x-ray exposure, two signals may beacquired from each camera by integrating over two separate intervalsthat are each approximately half of the x-ray exposure. During the firstinterval, the gain may be set to a relatively low gain and during thesecond interval, the gain may be set to a relatively high gain (or viceversa). As a result, each camera will capture image information in whichsubject matter of different densities are emphasized or suppressed.Thus, the information at each camera can be used to perform imageenhancement. Accordingly, image enhancement via gain variation may beperformed with or without multi-layer imaging by temporally obtainingimage information at different gains.

It should be appreciated that the exposure duration may be divided intoany number of different intervals to obtain as many or as few signalsfrom each camera during a single exposure. The gains assigned to theintervals may be chosen as desired to emphasize/suppress subject matteraccording to a particular imaging process. Other techniques may includeusing different gains with non-linear combinations of the multiplelayers to enhance or eliminate information related to a specificdensity. For example, such techniques may enable focusing on particularbiological structure such as obscuring or eliminating the ribcage in achest image while enhancing the soft tissue of the lungs or vice versa(i.e., enhancing the ribcage (hard tissue) and eliminating or reducingthe soft tissue). It should be further appreciated that the abovedescribed spatial and temporal gain variation techniques can be usedalone or in any combination, as the aspects are not limited in thisrespect.

Applicant has appreciated that the temporal aspect of the CMOS camerasmay be further utilized to perform dual energy or multiple energyimaging. Dual energy imaging exploits the physical phenomena that x-rayradiation of different energies will be absorbed differently by materialof different densities. Accordingly, if attenuation information isobtained from x-rays of different energies, the attenuation informationcan be compared to emphasize/suppress subject matter of selecteddensities. Applicant has appreciated that in many x-ray sources, thex-ray energies typically vary during power-up. That is, at the beginningof an exposure (i.e., when the x-ray source is first energized), thex-ray source electronics require some finite ramp-up time to reach fullpower. During the ramp-up interval, the energy in the x-rays isrelatively low and then increases over a power-up interval until thex-ray source has achieved steady-state and is operating at the nominalvoltage, current and/or power levels associated with the x-ray source.

Applicant has appreciated that by dividing up the interval over whichthe camera signal is integrated so that at least one interval generallycorresponds to the ramp-up period of the x-ray source, at least onecamera output will be representative of attenuation information of lowerenergy x-rays. One or more subsequent intervals may generally correspondto the steady state period of the x-ray source so that at least onecamera output will be representative of attenuation of higher energyx-rays. Having obtained attenuation information from at least twodifferent energy levels or ranges of energies, any of various dualenergy x-ray techniques may be applied to perform image enhancement. Itshould be appreciated that multiple intervals may be established duringthe ramp-up to obtain camera outputs during any number of intervals inthe duration in which the x-ray source is powering up. The differentenergies in such intervals may be used to obtain even richer attenuationinformation from a number of x-ray energies or ranges of x-ray energies.

Additionally, multi-layer imaging may also be utilized to perform dualenergy (or multiple energy) imaging. That is, the cameras in multiplelayers may be assigned different intervals during the exposure period tocollect attenuation information form x-rays of respectively differentenergies. For example, by operating the multiple cameras sequentially intime, a first set of cameras (e.g., associated with a first layer) willcapture data from the relatively low energy radiation associated withthe ramp-up interval, while a second set of cameras (e.g., associatedwith a second layer) will capture data from the relatively high energyradiation associated with the steady-state interval, thus obtainingseparate images at different radiation energies.

It should be appreciated that any number of sets of cameras may be used(e.g., any number of layers) to capture data at a respective differentradiation energy levels, as the aspects are not limited in this respect.The resulting images may be processed and manipulated in the same manneras other dual energy (or multiple energy) images to achieve the sameadvantages and/or benefits. It should be further appreciated that any ofthe above techniques may be used alone or in any combination, as theaspects are not limited in this respect or to any combination explicitlydescribed herein.

FIG. 8 illustrates a direct radiography device in accordance with someembodiments. DR device 800 includes a camera-based image sensor 810 forcapturing image information from an x-ray source. Camera-based imagesensor 810 may be any of the image sensors described herein capable ofcapturing image information by detecting radiation converted from thex-ray source, and at least comprises a plurality of cameras 805 (e.g.,an array of CMOS cameras) arranged to capture radiation down-converted(e.g., using an energy conversion component) from x-rays emitted from anx-ray source. The plurality of cameras 810 provide respective outputsindicative of the detected radiation to connection 820 to provide imagedata.

DR device 800 may also include computer 850 adapted to receive thesignal outputs from the image sensor. Computer 850 may include a memory855 and one or more processors 856 capable of accessing memory 855.Computer 850 is configured to received the data from the image sensorand to generate one or more images based on the data using processor(s)856 executing one or more algorithms stored in memory 855. Thus,computer 850 may be configured to process the data in any of the waysdiscussed herein (e.g., process overlap or multi-layer data, processspatially and/or temporally divided data, or any other image processingmethod described herein to produce one or more images of the objectexposed to the x-ray radiation). Computer 850 may perform otheroperations not specifically discussed herein to generate images from thecamera outputs.

Memory 855 may comprise any type of tangible, non-transitory computerreadable storage medium or storage device capable of storing data,instructions, etc, and may include ROM, RAM, disk storage, cache and/orany other storage medium, examples of which are provided below, and maybe implemented in any number of ways. Memory 855 may be encoded withinstructions, for example, as part of one or more programs that, as aresult of being executed by processor 856, instruct the computer toperform one or more of the methods or functions described herein, and/orvarious embodiments, variations and/or combinations thereof Memory 855may also store image data received by input 820 or otherwise stored incomputer 850.

Computer 850 may also be configured to operate the image sensor. Forexample, computer 850 may control which cameras are operating, mayset/apply gains to be used for each camera in the array, may establishthe one or more intervals over which the camera collects image data(e.g., for integration to produce an output), or may otherwise controlthe operation of image sensor 810. Computer 850 may include all of thenecessary electronics to interface with the camera array and thealgorithms to process the captured image data. However, computer 850need not include all of the above described functionality, but mayinclude some or all of the described control and processing capabilitiesof the DR device 800.

In some embodiments, DR device 800 also includes one or moreinput/outputs devices 822 capable of providing information external tothe DR device and/or capable of receiving information from one or moreexternal devices. For example, I/O device 822 may include an outputcapable or providing images produced by the DR device to an externalcomputer and/or display. Furthermore, I/O device 822 may include aninput that allows an external computer to control the image sensor. Forexample, in some embodiments, internal computer 850 may not beimplemented and/or some or all of the functionality described above asperformed by internal computer 850 may be performed by one or moreexternal computers such as a personal computer (PC), work station,general purpose computer, or any other computing device.

As such computer 850 may be integrated into DR device 800 or may be aseparate stand-alone system (or both), either proximate or remote fromDR device 800. For example, when external, computer 850 may be connectedto DR device 800 over a network and/or connected to multiple DR devices.For example, I/O device 822 may be configured to communicate with alocal computer or a remote computer either over physical connectionsand/or wirelessly. It should be appreciated that any computingenvironment may be used, as the aspects described herein are not limitedto use with a computer system of any particular type or implementation.

Some medical procedures use x-ray imaging technology to locate a regionof interest. In particular, since a region of tissue or organ ofinterest may be internal and cannot be seen during positioning, x-rayimaging is used. Conventionally, such procedures are performed using amechanical device called a “Bucky.” The Bucky is constructed as amagazine that a x-ray film cassette can be inserted into for taking oneor more x-ray exposures. The Bucky magazine can be moved manually underthe patient table in the XY plane parallel to the table top. Normally,the Bucky magazine is held tight in place by a breaking system and, whenrequired to be moved, the technician holds a special handle to releasethe breaks and move it as desired to position the cassette under thearea to be exposed. Motion of the magazine is achieved using an XYsystem comprising the necessary rails and chains. Under the magazinethere is a device called an Image Intensifier with its radiation inputside right under the Bucky's magazine. The image intensifier is a largeimage tube with special crystal scintillator at the front that transfersX-ray photons into electrons that are accelerated into small phosphorscreens with a video camera on its back end.

In a conventional procedure, a patient is set on the table and the x-raysystem is activated in a low dose mode while the Bucky mechanism ispositioned based on watching a video of the low dose images provided bythe image intensifier. The technician continues to operate the Buckymechanism until the region of interest or the desired body organ entersthe field of view and is positioned as desired. This procedure(fluoroscopy or flouro-mode) is performed under very low radiation andis used for positioning only where image quality may not be critical.Although the procedure is performed under very low radiation levels, itrequires the technician to position and move the Bucky manually,standing very close to the radiation source. As the desired position isachieved, the technician inserts the film or CR cassette into the Bucky,moves into the control room and provides a high energy radiography dose.The technician then may return to the Bucky to retrieve the cassette totransfer the cassette to the appropriate film processor or CR reader.This procedure is relatively inconvenient and may expose the technicianto radiation unnecessarily. When DR techniques are used, a relativelycomplicated mechanical engineering change typically must occur as themagazine that holds the cassette need to be changed to accept the muchthicker DR detector.

Applicant has appreciated that using camera array techniques as adetector may facilitate a more efficient, effective and safer medicalprocedure. In some embodiments, a camera-based image sensor as describedherein detector that is large enough to image a relatively substantialportion of a patient (or the entire patient as illustrated schematicallyin FIG. 9) is provided. This large area flat detector is part of the RFsystem table top and may be attached to its underside. The cameras inthis detector may have the ability to work in cine mode meaning thatthey can produce synchronized frames at, for example, 30 frames persecond. As a result, a real time video sequence of the exposure regionmay be produced. However, instead of having to manually maneuver theBucky system, a subset of the cameras may be operated to image aparticular region. This subset may then be varied (i.e., the subset ofcameras being operated may be changed by adding or removing cameras asdesired) until the proper subset of cameras is located that will imagethe desired region of the body. As shown in FIGS. 9A-9C by the blackcircles, the active cameras may be selectively operated until thedesired subset of cameras is located.

It should be appreciated that the selected area (e.g., the subset ofcameras to be operating at any given time) may be performed using touchpanel or joystick or any other suitable interface device. The selectedarea can be enlarged or minimized to the desired size and then be“moved” on the full area using the pointing device (touch screen,joystick or trackball), by adding and dropping tiles thus “moving”virtually the area of viewing onto the selected area of interest.

As described above, moving the selected area may be performed in lowdose mode and may be monitored via a video feed. It should beappreciated that the selected area can be enlarged, minimized and movedremotely such that the technician need not be near the radiation source.That is, the whole procedure may be performed remotely while thetechnician is in a control room using computer pointing device(touch-screen) without being exposed to radiation. When the desiredpositioning is achieved, the selected active detector area is switchedinto high radiography dose mode and the image of the desired region isacquired. The resulting image may appear immediately on the computerscreen in the control room enabling immediate quality control andadditional acquisition if required without moving the system or thepatient.

Applicant has further appreciated that the system described in theforegoing may be coupled with an overhead video camera to assistsurgeons in correctly identifying locations in which to operate. X-rayimages have conventionally been used to guide surgeons during anoperation or procedure. However, there is a limit to the usefulness ofusing just an x-ray image. In particular, it may be difficult tocorrectly identify the correct place to make an incision, insertarthroscopic equipment such as an endoscope, or otherwise enter the bodybased just on an x-ray image of the internal structure of the patient.This difficulty is exacerbated in overweight and obese patients.

By placing an overhead video camera at a known location, the videoimages may be mapped to the x-rays images obtained from the camera-basedsensor. The two images may be superimposed such that the surgeon canview the internal structures of the patient simultaneously and alignedwith the external video of the patient. As a result, the surgeon maymuch more easily identify insertion points and navigate during theoperation or procedure.

Applicant has appreciated that camera-based technologies may be used toconstruct large imaging areas. Since x-rays cannot be bent and there areno X-ray lenses, the X-ray films and today's CR cassettes and DRdetectors generally have the size of the organs to be exposed and thelarger standard area used is 17″×14″ (35 cm×43 cm). The relatively smallsize of these conventional detectors requires using a multitude ofstandard size film, cassettes over several exposures in order to imagelarge areas (e.g., a full body image). The images may then be stitchedtogether to enable the doctor to view the multiple images as one largeimage.

Applicant has appreciated that the relatively low cost element/camerasused in camera-based detectors renders the size of the detectorpractically limitless. Accordingly, camera-areas may be constructed tohandle large area imaging in a single exposure. Many imagingapplications require larger areas than available using standard medicalsizes. Camera-based detectors can be constructed at any size, allowingfor relatively simple, efficient and safe large area imaging. Theapplications for large area imaging are limitless, several applicationsof which are described in further detail below.

Medical “long bone” imaging comprises full leg imaging in a standingposition. This imaging procedure is used by orthopedics to view the legwhile standing under normal body load. Conventionally, this imagingprocedure is performed using a combination of three or more standardsizes cassettes wherein the results are “stitched” to enable the doctorto view the whole organ (e.g., the entire long bone). A singlecamera-based detector can perform the task with one single exposure andthe results may be viewed on the screen immediately. Spinal imaging isfrequently used in orthopedics to image the full length image of thespine such as in the case of scoliosis. Using a single camera-baseddetector, angle measurements may be improved since no stitching isrequired as in conventional imaging.

Emergency/military “whole body” imagine may be required in the case ofan emergency when victims/patients are brought into an emergencyfacility (e.g., a field facility). In such circumstances, the whole bodymay need to be imaged to quickly diagnose the full body for fractures orshrapnel. Conventionally, this procedure is performed using 12 to 14standard 14″×17″ exposures, which takes excessive time and is verycumbersome specifically under pressure of emergency and/or when multiplevictims need to be imaged. Camera-based detectors as described hereincan be used to produce an image of the entire body using a singleexposure, and without the need to keep track of which portion of thebody has been imaged and which has not, and which cassettes and theassociated sub-images belong to which victim.

Veterinary images, for example, for equine may require large imagingareas. For example, imaging a horse's legs is a routine for an equineveterinarian. However, this is an intense labor task. This task is oftenperformed in the field and requires multiple exposures since the legsare long and the detector's size is small. DR systems are not designedfor field use and their cost may make them impractical for this task.Camera-based detectors described herein can provide the full length ofthe horse's leg in a single exposure. Large pets such as a large dog orany other large animal is problematic because they move and their sizemakes the full body exposure a complicated task. Such an imaging taskcan be achieved by a large dedicated camera-based detector.

In industry and/or security, nondestructive testing of large objects mayneed to be performed. When large objects need to be exposed, very largecamera-based detectors can be designed. For example, ship containers canbe exposed in one exposure by a container size camera-based detector. Inairports, even very large luggage can be exposed in a single exposureusing camera-based detector technology. Other applications requiringlarge imaging areas may equally benefit from the camera-based imagingtechniques described herein, and the aspects are not limited for usewith any particular application.

Various aspects of the present invention may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in its application to the details and arrangement of componentsset forth in the foregoing description. The above-described embodimentscan be implemented in any of numerous ways. For example, the embodimentsmay be implemented using hardware, software or a combination thereof.When implemented in software, the software code can be executed on anysuitable processor or collection of processors, whether provided in asingle computer or distributed among multiple computers.

It should be appreciated that any component or collection of componentsthat perform the functions described above can be generically consideredas one or more controllers that control the above-discussed function.The one or more controller can be implemented in numerous ways, such aswith dedicated hardware, or with general purpose hardware (e.g., one ormore processor) that is programmed using microcode or software toperform the functions recited above. The controller may be part of oneor more computers that are programmed to perform the associatedfunction.

It should be appreciated that the various methods outlined herein may becoded as software that is executable on one or more processors thatemploy any one of a variety of operating systems or platforms.Additionally, such software may be written using any of a number ofsuitable programming languages and/or conventional programming orscripting tools, and also may be compiled as executable machine languagecode. In this respect, it should be appreciated that one embodiment ofthe invention is directed to a tangible, non-transitory computerreadable storage medium (or multiple such computer readable storagemedia) (e.g., a computer memory, one or more floppy discs, compactdiscs, optical discs, magnetic tapes, etc.) encoded with one or moreprograms that, when executed on one or more computers or otherprocessors, perform methods that implement the various embodiments ofthe invention discussed above. The computer readable storage medium ormedia can be transportable, such that the program or programs storedthereon can be loaded onto one or more different computers or otherprocessors to implement various aspects of the present invention asdiscussed above.

It should be understood that the term “program” is used herein in ageneric sense to refer to any type of computer code or set ofinstructions that can be employed to program a computer or otherprocessor to implement various aspects of the present invention asdiscussed above. Additionally, it should be appreciated that accordingto one aspect of this embodiment, one or more computer programs thatwhen executed perform methods of the present invention need not resideon a single computer or processor, but may be distributed in a modularfashion amongst a number of different computers or processors toimplement various aspects of the present invention.

Various aspects of the present invention may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in its application to the details and arrangement of componentsset forth in the foregoing description or illustrated in the drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

Use of ordinal terms such as “first”, “second”, “third”, etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing”, “involving”, andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

1. A device comprising: a plurality of cameras; an energy conversioncomponent capable of converting first radiation at a first energy tosecond radiation at a second energy lower than the first energy; and atleast one refraction component positioned between the energy conversioncomponent and the plurality of cameras, the refraction component adaptedto reflect at least some of the second radiation emitted by the energyconversion component above a critical angle away from the plurality ofcameras and to refract at least some of the second radiation emitted bythe energy conversion component below the critical angle ontocorresponding cameras of the plurality of cameras.
 2. The device ofclaim 1, wherein each of the plurality of cameras, arranged in an array,produce a signal indicative of radiation impinging on the respectivecamera, the plurality of cameras arranged such that the field of view ofeach of the plurality of cameras at least partially overlaps the fieldof view of at least one adjacent camera of the plurality of cameras, toform a respective plurality of overlap regions, the device furthercomprising: at least one computer for processing the signals from eachof the plurality cameras to generate at least one image, the at leastone processor configured to combine signals in the plurality of overlapregions to form the at least one image.
 3. The device of claim 2,wherein the at least one computer sums signals in corresponding overlapregions to increase the signal-to-noise ratio.
 4. The device of claim 2,wherein the plurality of cameras includes a plurality of sets of camerascomprising at least a first set of cameras to provide signalscorresponding to a first image layer and a second set of cameras toprovide signals corresponding to a second image layer, the first set ofcameras and the second set of cameras positioned relative to one anothersuch that the field of view of the first set of cameras overlaps withthe field of view of the second set of camera such that the first imagelayer and the second image layer include data corresponding tosubstantially the same field of view.
 5. The device of claim 4, whereinthe at least one computer is configured to combine at least the firstimage layer and the second image layer to form, at least in part, the atleast one image.
 6. The device of claim 5, wherein the at least onecomputer is configured to sum at least the first image layer and thesecond image layer to, at least in part, form the image.
 7. The deviceof claim 5, wherein the at least one computer is configured to performan average and/or a weighted average of at least the first image layerand the second image layer to, at least in part, form the at least oneimage.
 8. The device of claim 4, wherein the at least one computer isconfigured to establish a gain for each of the plurality of cameras. 9.The device of claim 2, wherein the plurality of sets of camerascomprises more than two sets of cameras to produce more than two imagelayers.
 10. The device of claim 1, wherein the plurality of cameras areCMOS cameras.
 11. The device of claim 1, further comprising at least oneblocking component positioned between the energy conversion componentand the plurality of cameras to block at least some of the firstradiation that passes through the energy conversion componentunconverted.
 12. The device of claim 11, wherein the blocking componentincludes at least one of a leaded glass or a lead coating.
 13. Thedevice of claim 11, wherein the at least one blocking component includesa blocking layer over each lens of the plurality of cameras.
 14. Thedevice of claim 11, wherein the refraction component includes theblocking component by using a high refraction leaded glass layer or byforming on the refraction component a leaded glass coating.
 15. Thedevice of claim 11, wherein the refraction layer and the blockingcomponent are separate.
 16. The device of claim 1, wherein each of theplurality of cameras is a CMOS camera.
 17. A device comprising: aplurality of cameras arranged in an array, each of the plurality ofcameras producing a signal indicative of radiation impinging on therespective camera, the plurality of cameras arranged such that the fieldof view of each of the plurality of cameras at least partially overlapsthe field of view of at least one adjacent camera of the plurality ofcameras, to form a respective plurality of overlap regions, wherein theplurality of cameras includes a plurality of sets of cameras comprisingat least a first set of cameras to provide signals corresponding to afirst image layer and a second set of cameras to provide signalscorresponding to a second image layer, the first set of cameras and thesecond set of cameras positioned relative to one another such that thefield of view of the first set of cameras overlaps with the field ofview of the second set of camera such that the first image layer and thesecond image layer include data corresponding to substantially the samefield of view; an energy conversion component for converting firstradiation impinging on a surface of the energy conversion component tosecond radiation at a lower energy that is detectable by the pluralityof cameras; and at least one computer for processing the signals fromeach of the plurality cameras to generate at least one image, the atleast one processor configured to combine signals in the plurality ofoverlap regions to form the at least one image, wherein the at least onecomputer is configured to vary at least one of the gains of at least oneof the plurality of cameras based, at least in part, on whether the atleast one of the plurality of cameras is in the first set of cameras orthe second set of cameras.
 18. A device comprising: a plurality ofcameras arranged in an array, each of the plurality of cameras producinga signal indicative of radiation impinging on the respective camera, theplurality of cameras arranged such that the field of view of each of theplurality of cameras at least partially overlaps the field of view of atleast one adjacent camera of the plurality of cameras, to form arespective plurality of overlap regions, wherein the plurality ofcameras includes a plurality of sets of cameras comprising at least afirst set of cameras to provide signals corresponding to a first imagelayer and a second set of cameras to provide signals corresponding to asecond image layer, the first set of cameras and the second set ofcameras positioned relative to one another such that the field of viewof the first set of cameras overlaps with the field of view of thesecond set of camera such that the first image layer and the secondimage layer include data corresponding to substantially the same fieldof view; an energy conversion component for converting first radiationimpinging on a surface of the energy conversion component to secondradiation at a lower energy that is detectable by the plurality ofcameras; and at least one computer for processing the signals from eachof the plurality cameras to generate at least one image, the at leastone processor configured to combine signals in the plurality of overlapregions to form the at least one image, wherein the at least onecomputer is configured to assign each camera in the first set of cameraswith a first gain and each camera in the second set of cameras with asecond gain that is different than the first gain.
 19. The device ofclaim 18, wherein the at least one computer is configured to combine thefirst layer obtained at the first gain with the second layer obtained atthe second gain to emphasize at least some subject matter of interest inthe image.
 20. The device of claim 18, wherein the at least one computeris configured to combine the first layer obtained at the first gain withthe second layer obtained at the second gain to suppress at least somesubject matter of interest in the image.
 21. A device comprising: aplurality of cameras arranged in an array, each of the plurality ofcameras producing a signal indicative of radiation impinging on therespective camera, the plurality of cameras arranged such that the fieldof view of each of the plurality of cameras at least partially overlapsthe field of view of at least one adjacent camera of the plurality ofcameras, to form a respective plurality of overlap regions; an energyconversion component for converting first radiation impinging on asurface of the energy conversion component to second radiation at alower energy that is detectable by the plurality of cameras; at leastone computer for processing the signals from each of the pluralitycameras to generate at least one image, the at least one processorconfigured to combine signals in the plurality of overlap regions toform the at least one image, wherein the at least one computer isconfigured to establish a gain for each of the plurality of cameras, andwherein the at least one computer varies the gain of at least one cameraover a designated interval.
 22. The device of claim 21, wherein the atleast one computer is configured to establish a first gain for each ofthe plurality of cameras for a first portion of the designated intervaland establish a second gain for each of the plurality of cameras for asecond portion of the designated interval.
 23. A device comprising: aplurality of cameras arranged in an array, each of the plurality ofcameras producing a signal indicative of radiation impinging on therespective camera, the plurality of cameras arranged such that the fieldof view of each of the plurality of cameras at least partially overlapsthe field of view of at least one adjacent camera of the plurality ofcameras, to form a respective plurality of overlap regions; an energyconversion component for converting first radiation impinging on asurface of the energy conversion component to second radiation at alower energy that is detectable by the plurality of cameras; at leastone computer for processing the signals from each of the pluralitycameras to generate at least one image, the at least one processorconfigured to combine signals in the plurality of overlap regions toform the at least one image, wherein the at least one computer isconfigured to receive a plurality of signals from each of the pluralityof cameras over a designated interval, and wherein at least one of theplurality of signals from each of the plurality of cameras is associatedwith a first portion of the designated interval, and at least one of theplurality of signals from each of the plurality of cameras is associatedwith a second portion of the designated interval.
 24. The device ofclaim 23, wherein the first portion of the designated interval isassociated with at least part of a power-up interval of an x-ray source,and the second portion of the designated interval is associated with atleast part of a powered-up interval of the x-ray source.
 25. A methodcomprising: converting first radiation at a first energy to secondradiation at a second energy lower than the first energy; reflecting atleast some of the second radiation away from a plurality of cameras; andrefracting at least some of the second radiation onto correspondingcameras of the plurality of cameras.
 26. The method of claim 25 furthercomprising: receiving at least some of the second radiation atcorresponding ones of the plurality of cameras, arranged in an array,each of the plurality of cameras producing a signal indicative ofradiation impinging on the respective camera, the plurality of camerasarranged such that the field of view of each of the plurality of camerasat least partially overlaps the field of view of at least one adjacentcamera of the plurality of cameras, to form a respective plurality ofoverlap regions; and processing the signals from each of the pluralitycameras to generate at least one image, the at least one processorconfigured to combine signals in the plurality of overlap regions toform the at least one image.
 27. The method of claim 25, furthercomprising blocking at least some of the first radiation that is notconverted to second radiation.